The important relation which a well ventilated dark-room bears to results is perhaps not always fully appreciated. Numerous troubles which occur and the cause of which seems hard to locate and difficult to explain, are really attributable to poorly ventilated dark or work rooms and would readily disappear if better atmospheric conditions were afforded. This is particularly true in dry plate manipulation and very often frilling and softening of the emulsion is due to no cause other than working in a close, stuffy room.

Photographic emulsions are subjected to hard usage and are frequently abused. The sensitized emulsions of dry plates and papers are extremely delicate and are subject to injury from many causes. When the product goes to pieces under severe treatment the manufacturer is very likely blamed. This, of course, is often a very serious matter with the photographer and sometimes the manufacturer replaces the goods complained of, as a matter of courtesy, though feeling very sure that such goods were not faulty. Most troubles with sensitized goods, however, are found to be due to improper manipulation and to local conditions prevailing in customers' own work rooms.

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Fig. 1.

Important among obscure causes is a lack of ventilation.

The problem which arises is how to ventilate - how to obtain a free circulation of air and still exclude light. In the case of a small dark-room inconveniently placed as regards outside walls this is rather a difficult matter. In the case of the newer and more modern studio buildings, an increasing number of which are being constructed, the problem of ventilation is taken care of in the original plans by a competent architect. We will, therefore, take up the question of how to ventilate the ordinary dark-room which was not properly planned when built.

The logical thing is to induce a circulation of air toward the top of the room, as warm air and impure gases will rise toward the ceiling. Usually an opening cut in the wall or partition near the floor and another similar opening near the ceiling and on the opposite side, if possible, will give a good current of air. To exclude light both openings should be constructed with a "light lock" or "light trap." This is better illustrated than explained, and Fig. 1 will show what is meant. A similar opening should be placed opposite near the ceiling.

If the dark-room is provided with a "light lock" entrance, and for this reason has an ample ingress of air, a single opening for egress near the ceiling would be required. The circulation of air can be advantageously accelerated by an electric fan so placed in the upper opening as to draw the air out of the room.

If the dark-room is on the upper floor two or more revolving ventilators on the roof would take the place of upper wall ventilator. Fig. 2 illustrates this.

The air currents can be regulated by means of shut-offs operated by a cord or chain so that in cold weather too much circulation can be retarded. If dust is found to enter by ventilation openings, muslin stretched over frames should be placed over the openings.

The simplest form of improvised ventilator would be a length of ordinary sheet iron stove pipe with a double elbow leading out from near the ceiling. Cut No. 3 illustrates this.

Too much emphasis cannot be placed on the fact that many of the unexplainable difficulties which sooner or later confront the photographer, are attributable to excessive humidity or incorrect temperature. These conditions can be largely overcome by proper ventilation.

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Fig. 2.

From An Artura Iris Print By E. L. Mix New York.

From An Artura Iris Print By E. L. Mix New York.

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Fig. 3.